Furthermore, the heart is composed of many cell types, the most abundant being cardiomyocytes, fibroblasts, endothelial cells, and peri-vascular cells.25 Both cardiomyocytes and non-cardiomyocytes respond to physiological and pathological stress, and maladaptive changes in non-cardiomyocytes participate in the pathogenesis of heart failure.25 As PCSK9 is expressed in many cell types, cardiomyocyte-specific Pcsk9-deficient mice are needed to clarify the specific role of PCSK9 for cardiac function. Here, PCSK9 is linked to heart failure.